Here is an example.
We have A7s (hearts) UtG. We open 3x and get called by the button. Flop is KT4 with 2 diamonds, no heart. Our best move here is to just check-fold to a c-bet and give up. This is why A7s is generally not considered in an early position open range. We are playing out of range here and got ourselves into trouble. And this flop is very normal and common that we will see. We will get ourselves into trouble very often by opening (a hand like) A7s out of position. All we have here is an overcard. We are very weak.
Now, same A7s (hearts) but from the BT this time. 2 limpers and we open 3x. One limper calls. Same flop KT4 with 2 diamonds and no heart.
spot #1: Villain checks. We can simply c-bet this for 40-60% pot (I usually use about 40% myself) and it is highly likely that Villain folds right here and we win with NOTHING (haha!).
Spot #2: Same flop, Villain donks min. We can simply fold, or since it's such a small bet we can call this because it is very likely a blocker (draw) or a feeler and we can call/float to play the turn. Then if Villain checks the turn is very likely that it was just a feeler and now he's ready to give up, especially if the turn card does not help any draws. We can bet the turn half-pot-ish and he will very likely fold. If Villain continues on the turn we can decide to fold or call depending on the board and Villain's tendencies (poker sense).
Spot #3: Villain donks large. We have an easy fold and Villain can't get paid.
So we can see here that there are just so many more options for us when we are in position than when we are out of position.
And these examples are only WHIFFED flops! Just think of what we can do if we actually HIT. $ $ $ $ cha-ching! cha-ching!